1. Field of the Invention
The present invention relates to an endoscopic sheath used in combination with an endoscope for observing the interior of a body cavity.
2. Description of the Related Art
Conventional sheaths to be fitted on the insert section of endoscopes have various configurations depending on the purpose of application.
Described in Jpn. Pat. Appln. KOKOKU Publication No. 4-10328, for example, is a sheath which enables a direct endoscopic observation of subcutaneous tissue or any other desired portion of a living body in which no spaces exist. This sheath is a rigid guide tube through which an endoscope is passed and guided to a target region in a patient's body. The distal end of the sheath is closed, and at least part of it is formed of a material which transmits light. As this sheath is inserted into subcutaneous tissue or other organic portion without spaces, it thrusts aside the organic portion, thereby positively creating a space in the region. Thus, by passing the endoscope through the sheath kept in the subcutaneous tissue, for example, the tissue can be subjected to endoscopic observation through the transparent guide tube portion.
Disclosed in Jpn. UM Appln. KOKOKU Publication No. 4-43202, moreover, is a tubular protective sheath which is fitted on an insert section of an endoscope to protect the endoscope. This sheath enables endoscopic observation through its distal opening. A stopper for preventing projection of the endoscope is provided on that part of the distal end portion of the sheath which does not interfere with the view range of the endoscope. The stopper can prevent the endoscope from projecting from the distal end of the sheath without the possibility of the distal end edge of the sheath or the like interfering with the view range of the endoscope. Thus, the entire view range can be utilized, and the distal end portion of the endoscope can be prevented from being damaged.
The sheath used with the endoscope in this manner is expected to facilitate accurate observation of the state of a subject tissue by means of the endoscope, without interfering with the view range of the endoscope, and to be smoothly inserted together with the endoscope into a patient's body without injuring the patient.
Since the sheath described in Jpn. Pat. Appln. KOKOKU Publication No. 4-10328 is formed as a rigid body including the transparent portion for observation, however, the subject tissue is pressed by the sheath, so that it is hard to observe the color and shape of the tissue accurately. In case of bleeding, moreover, the pressure exerted on the subject tissue by the sheath makes the spot of bleeding obscure, making it difficult to determine and perform the appropriate treatment.
According to the arrangement described in Jpn. UM Appln. KOKOKU Publication No. 4-43202, on the other hand, the endoscopic observation of tissue can be achieved through the distal opening of the sheath, so that the subject tissue is not be pressed by the sheath. Accordingly, this sheath is not subject to the aforesaid problems. Since the sheath cannot be situated within the view range of the endoscope, however, the degree of contact between the distal end portion of the sheath and the living tissue cannot be detected, so that the pressure of the sheath end portion on the tissue cannot be identified. Thus, the sheath cannot be smoothly inserted into a patient's body without injuring the patient.